Fabrication method for microstructures with high aspect ratios

Abstract

A fabrication method for microstructures with high aspect ratios is defined using via plugs and contact plugs. An etching channel is shaped as the microstructure is formed. Finally, an isotropic etching process is employed to remove the silicon substrate under the microstructure, thereby making a suspending microstructure with a high aspect ratio. In comparison with the prior art, the invention can save many photolithography steps and can be readily integrated into existing processes. Therefore, one can use the existing IC manufacturing equipment to make suspending microstructures with high aspect ratios.

What is claimed is:  
     
         1 . A fabrication method for making a microstructure with a high aspect ratio, the method comprising the steps of: 
 providing a substrate;    depositing in order a plurality of dielectric layers, a plurality of metal layers, and a plurality of polysilicon layers to form a microstructure and a contact plug;    wherein the plurality of metals are connected using a plurality of via plugs and the via plugs are not inserted with metal, forming an etching channel; and    etching through the etching channel the substrate under the microstructure so that the microstructure suspends and has a high aspect ratio.    
     
     
         2 . The fabrication method of  claim 1 , wherein the substrate is a silicon substrate.  
     
     
         3 . The fabrication method of  claim 1 , wherein the dielectric layers are silicon dioxide dielectric layers.  
     
     
         4 . The fabrication method of  claim 1 , wherein the plurality of metal layers are formed from aluminum, copper and their alloys.  
     
     
         5 . The fabrication method of  claim 1 , wherein the etching channel is completed using an anisotropic etching process.  
     
     
         6 . The fabrication method of  claim 1 , wherein the step of etching through the etching channel the substrate under the microstructure employs an isotropic etching process.  
     
     
         7 . The fabrication method of  claim 1 , wherein the step of etching through the etching channel the substrate under the microstructure employs one method selected from dry etching and wet etching.  
     
     
         8 . The fabrication method of  claim 7 , wherein the etchant of the wet etching is a sulfuric acid etchant formed with an appropriate ratio.  
     
     
         9 . The fabrication method of  claim 7 , wherein the etching gas in the dry etching is one selected from SF 6  and XeF 2 .